Stack of elongate elements in a container and method of stacking

ABSTRACT

A stack of elongate elements, such as lengths pipes, in a container, such as a gondola railroad car, that has an interior length greater than the length of the individual pipes. The pipes are stacked so that some of the pipes in the stack have end portions adjacent one end of the container and other pipes have end portions adjacent the other end of the container, such that the stack has an overall length approximating the interior length of the container. End lashings are secured around the end portions of the pipes and apply a pinching pressure to the end portions. A plurality of interior lashings are secured around the pipes interiorly of the end portions with each interior lashing including at least one pipe that is also included within another interior lashing.

FIELD OF THE INVENTION

The present invention relates to a stack of elongate elements in a container and to a method of stacking. More particularly, the present invention relates to stacking of elongate elements in a container having an interior length greater than the length of the individual elements with the individual elements stacked in a manner that provides a stack having an overall length approximating the interior length of the container.

BACKGROUND OF THE INVENTION

Elongate elements, such as lengths of pipe or other types of cylindrical conduits or rods, are commonly loaded in containers for shipment, such as in gondola railroad cars or open top truck beds. Usually, the elements are of lengths less than the interior length of the container. As a result, during transport when there is abrupt stopping and starting, such as during the back-and-forth stopping and starting of railroad freight cars in a hump yard in making up a train, the elements in the stack shift suddenly and potentially cause damage to the ends of the container and disrupt the relative position of the elements in the stack. It is known to stack railroad ties in the ends of the cars to fill the space between the ends of the pipes and the end wails of the car. Also, it is known to use steel or fabric lashings encircling stacks of pipes in gondola cars to restrict lengthwise shifting of the pipes, such as disclosed in AAA Open Top Loading Rules Manual (12/2007), pages 236-241, but such lashings do not provide sufficient restraint to reliably prevent damaging shifting. It is to solving this problem that the present invention is directed.

SUMMARY OF THE INVENTION

The present invention provides a solution to the problem of shifting of elements in a container causing damage to the ends of the container in which they are stacked.

Briefly described, in one form, the stack of the present invention is formed from horizontal lengths of elongate elements of substantially equal length disposed for stacking in a container having an interior length greater than the lengths of the individual elements. The elements are stacked in horizontal rows with the end portions of one row or rows extending beyond the ends of another row or rows, so that the end portions of a row or rows is adjacent one end of the container and the opposite end portions of another row or rows is adjacent the other end of the container. Means, such as lashings encircling the stack, are provided for restraining lengthwise movement of the rows of elements. With this arrangement, the close proximity of the ends of rows to the opposite end walls of the container precludes damaging shifting of the elements during sudden stopping of the container.

Preferably, the stack includes a first row or rows of elements having end portions adjacent one end of the container, a second row or rows of elements having end portions adjacent the opposite end of the container, a third row or rows of elements vertically aligned with the first row or rows and a fourth row or rows of elements vertically aligned with the second row or rows. A lashing is secured around the extending end portions of the first and third row or rows and a lashing is secured around the extending end portions of the second and fourth row or rows. The lashings are sufficiently tight to apply a slight pinching of the end portions against the adjacent row or rows to resist relative longitudinal shifting of adjacent rows, but not sufficient to cause any significant deformation of the end portions.

In a more detailed preferred embodiment of the stack of the present invention, there is added a top row or rows of elements stacked on top of the other rows and generally longitudinally centered with respect to the combined length of the rows of elements therebelow. This top row or rows of elements is included within the lashings that encircle the other rows of the stack and is above the height of the end walls of the container such that the top row or rows will not impact the container end walls upon slight shifting of the top row or rows.

The elements may be cylindrical with at least two rows of adjacent elements arranged in a nesting pair or pairs and at least one mat of slip resisting material positioned between the rows of the nesting pair or pairs. Spacer bars may be disposed laterally under the lowermost row of the stack and between at least two rows of elements, to provide access for unloading. The intermediate lashings extend through the spaces provided by the spacer bars.

In broad terms the method of Loading a stack according to the present invention includes loading horizontal rows of elements of substantially equal length in a container having upstanding end walls spaced apart a distance greater than the length of the elements. A first horizontal row or rows of elements is loaded into the container with one end portion at one end thereof adjacent one end wall of the container. A second horizontal row or rows of elements is then loaded into the container with one end portion adjacent the opposite end wall of the container. Means for restraining significant relative lengthwise movement of the rows of elements is then applied.

In a more detailed preferred embodiment of the method of loading a stack, the loading begins by placing a plurality of spaced laterally extending spacer bars on the container bottom, then placing laterally extending lashings on the container bottom for subsequent lashing together of rows of elements. A first row or rows of elements is loaded on the bottom spacer bars with one end portion adjacent one end wail of the container and the other end spaced from the opposite end wall of the container. A second row or rows of elements is then loaded on top of the first row or rows with end portions adjacent the opposite end wall of the container. A third row or rows of elements is loaded on top of the second row or rows with end portions aligned longitudinally with the end portions of the first row or rows, and a fourth row or rows of elements is loaded on top of the third row or rows with end portions aligned with the end portions of the second row or rows. A lashing is applied around the end portions of the first and third rows and a lashing is applied around the end portions of the second and fourth rows. During this loading, laterally extending, longitudinally spaced, spacer bars and lashings are placed between at least some rows of elements. During sequential loading of rows of elements the previously laid lashings are secured around a plurality of rows of elements including rows above subsequently laid lashings.

The method of loading may include the further loading of a plurality of upper rows of elements generally centrally disposed between the end walls of the container, with the aforementioned placing of spacer bars and lashings and securing of lashings continuing through the loading of the upper rows of elements.

In the preferred embodiment the elements are cylindrical, such as pipes, and the method of loading includes laying a plurality of the elements in nested pairs while placing mats of slip resistant material between the rows in the nested pairs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a stack of pipes of the preferred embodiment of the present invention shown loaded in a gondola railroad car, with the adjacent side of the car removed for clarity;

FIGS. 2-16 are perspective views illustrating the sequence of loading of pipes in a gondola railroad car according to the preferred embodiment of the method of the present invention with the end and side walls of the railroad car shown only in dot-dash lines for clarity of illustration of the loaded stack; and

FIG. 17 is a perspective view of a completed stack of the present invention in a gondola railroad car.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Following is a detailed description of a stack and method of stacking of a typical embodiment of the present invention incorporating the various features of the invention.

The stack 20 of elongate elements in the form of cylindrical pipes 22 is illustrated in the drawings loaded in an open top gondola railroad car G that has a bottom B, on which the stack 20 is loaded, side walls 5, and end walls E and F. Normally, the length of the pipes is less than the interior length between the gondola car's end walls E and F. Four spaced vertical posts P are secured along each side wall S of the car to retain the stack 20 in place.

Nine longitudinally spaced bottom spacer bars 24 extend transversely across the gondola car bottom B between the side walls S. A first two nesting rows 26, 27 of pipes P are stacked on the bottom spacer bars 24 with end portions 28 at one end adjacent one end wall E and their other ends 29 spaced from the other end wall F of the gondola car G.

Nine longitudinally spaced spacer bars 30 are disposed laterally on the first two rows 26, 27 of pipes 22. A second two nesting rows 32, 33 of pipes P are stacked on the spacer bars 30 with end portions 34 at one end adjacent the other end wall F and their other ends 35 spaced from the one end wall E. In combination, the overall length of the stacked pipes P approximates the interior length of the gondola car G.

Nine longitudinally spaced spacer bars 36 are disposed laterally on the second two rows 32. 33 of pipes P. A third two nesting rows 38, 39 of pipes P are stacked on the spacer bars 32 aligned lengthwise with the first two rows 26, 27 of pipes P, having end portions 40 aligned with the end portions 28 of the first two rows 26, 27 of pipes P and other ends 41 aligned with the other ends 29 of the first two rows 26, 27.

A first end lashing 42 extends laterally under the end portions 28 of the first two rows of pipes 26, 27 and over the end portions 40 of the third two rows of pipes 38, 39. This first end lashing 42 is secured by a buckle 44 (FIG. 8) around the end portions 28 and 40 sufficiently tight to apply a slight pinching of the end portions against adjacent rows of pipes to resist relative lengthwise shifting of the adjacent rows of pipes, but not sufficient to cause any significant deformation of the end portions.

Nine longitudinally spaced spacer bars 45 are disposed laterally on the third two rows 38, 39 of pipes. A fourth two nesting rows 46, 47 of pipes P are stacked on the spacer bars 36 aligned lengthwise with the second two rows 32, 33 of pipes, having end portions 48 aligned with the end portions 34 of the second two rows 32, 33 of pipes and other ends 49 aligned with the other ends 41 of the second two rows.

A second end lashing 50 extends laterally under the end portions 34 of the second two rows 32, 33 of pipes P and over the end portions 48 of the fourth two rows 46, 47 of pipes. This second end lashing 50 is secured by a buckle 44 (FIG. 10) around the end portions 34 and 48 sufficiently tight to apply a slight pinching of the end portions against adjacent rows of pipes to resist relative lengthwise shifting of the adjacent rows of pipes, but not sufficient to cause any significant deformation of the end portions.

Nine longitudinally spaced spacer bars 51 are disposed laterally on the fourth two rows 46, 47 of pipes. Three nesting pairs of top rows 52, 53, 55, 57, 59 and 61 of pipes P are stacked on top of the spacer bars 51 above the other rows and generally longitudinally centered with respect to the combined length of the rows of pipes therebelow. Typically the centered top rows are above the height of the end walls E and F of the gondola car G, where abutting the end walls is not a problem.

Nine longitudinally spaced spacer bars 54 are disposed between the pairs of top rows 52, 53, 55, 57 and 61. These top rows are above the height of the end walls E and F of the gondola car G and both ends of the pipes of the top rows are longitudinally spaced from the end walls of the car, so that shifting of the top rows due to abrupt stopping and starting of the car will advantageously not result in the ends of the pipes of the upper rows from extending beyond the end walls of the car.

Four longitudinally spaced mats 56 of slip resisting material are disposed between the rows of the third nesting pair of rows 38, between the rows of the fourth nesting pair of rows 46 and between the rows of pipes of each pair of top rows 52, 53, 55, 57 and 61. These mats 56 assist in resisting longitudinal movement of the adjacent rows upon abrupt stopping and starting of the gondola ear G.

A plurality of interior lashings combine to form an overlapping network of lashings that confines the pipes in the stacked configuration. These interior lashings extend through the spaces provided by the spacer bars. These interior lashings include a bottom lashing 58 secured around the first, second and third pairs, 26, 27, 32, 33 and 38, 39, of rows of pipes. Three spaced lashings 62 are secured around the third and fourth pairs, 38, 39, 46, 47 rows of pipes and the first pair 52, 53 of top rows of pipes. Three spaced lashings 64 are secured around the fourth pair 46, 47 and the first pair 52, 53 of top rows. Three spaced lashings 66 are secured around the fourth pair 46, 47 and the first two pairs 52, 53, 55, 57 of top rows of pipes. Three spaced lashings 68 are secured around the lower two pairs 52, 53, 55, 57 of top rows of pipes. Three spaced lashings are secured around the top two pairs 55, 57, 59, 61 of top rows of pipes. Each of these interior lashings is secured by a buckle 44.

With this arrangement of interior lashings, at least one of the interior lashings extends under the lowermost row of pipes, at least one other interior lashing extends over the top row of pipes and under at least one row of pipes therebelow, and other interior lashings are each secured around a plurality of rows of pipes that includes one row that is also secured within at least one of the other interior lashings. This creates a strong confinement network of lashings to hold the pipes in the stacked configuration. While particular lashing arrangements are disclosed, variations may be utilized as well, provided there is a sufficient number of lashings in overlapping relation to tie the pipes together in a firm stack.

To prevent spreading apart laterally of the vertical posts P and to facilitate retention of the stack 20 in place, the posts are arranged in lateral pairs with each pair having a post on each opposite side of the gondola car G, and cross-retaining lashings 74 are looped around each pair of posts across rows of pipes with the ends of the lashings secured by buckles 44. These cross-retaining lashings 74 are disposed above each pair of top rows of pipes and between the nested pipes of the top pair of the top rows of pipes.

In a typical commercial application of the preferred embodiment of the present invention, the pipe stack 20 is loaded in a gondola freight car G that extends 52 feet between the end walls E and F, with side walls S that extend upward 5 feet above the bottom B of the car G. The vertical posts P are wooden 4×4s. The pipes 22 are, for example, steel pipes of 3 to 11 inches in diameter, commonly 5½ inches, and 42 to 48 inches in length. Commonly, there are 40 or more pipes 22 in a typical stack 20 and the stack is typically about 9 feet high. Typically, the section of pipes that have pipes with end portions extending beyond the ends of other pipes amounts to about 60% of the height of the stack, and the top rows of the stack, amount to about 40% of the height of the stack. The lashings may be woven polyester fabric 1⅝ inches thick, such as sold by Carolina Strapping and Buckles Company of Gastonia, N.C. The slip-resistant mats 56 are made of rubber, or similar material, and are typically ⅛ of an inch thick and 18 inches wide. The spacer bars 30, 36, 45, 51 and 54 are typically wooden 2×4s.

The method of the preferred embodiment of the present invention begins (FIG. 2) with attaching the vertical posts P to the side walls S of a gondola railroad car G. Then nine longitudinally spaced bottom spacer bars 24 are placed transversely on the bottom B of the car G. A bottom interior lashing 58 is placed across the bottom B of the car G in the general area of the middle of the car G. This bottom interior lashing 58 has ends draped over the side walls S of the car G. Also, first and second end lashings 42 and 50 are placed across the bottom B near the ends of the car G with their ends draped over the side walls S.

The rows of the first two rows 26, 27 of pipes are individually laid on the bottom spacer bars 24 with end portions 28 abutting one end wall E of the car G and the other ends 29 spaced from the other end wail F of the car G (FIGS. 3 and 4). Typically the rows of pipes are loaded using a magnetic loader or a fork lift.

As illustrated in FIG. 4, nine spaced spacer bars 30 are placed across the first two rows 26, 27 of pipes and three spaced interior lashings 60 are placed across the first two rows 26, 27 of pipes and draped over the side walls S of the car G.

As illustrated in FIGS. 5 and 6, the pipes of the second two rows 32, 33 of pipes are individually laid on top of the spacer bars 30 with end portions 34 abutting the other end wall F of the car G and their other ends 32 spaced from the one end wall E of the car G. Nine spaced spacer bars 36 and four spaced interior lashings 62 are then placed across the top of the second two rows 32, 33 of pipes, with ends of the lashings draped over the side walls S of the car G.

As illustrated in FIG. 7, the first row 38 of the third two rows 38, 39 of pipes is laid on top of the spacer bars 32 that are on top of the second two rows 32, 33 of pipes with end portions 40 abutting the one end wail E of the car G. Four longitudinally spaced slip-resisting mats 56 are placed on top of the first row 38 of the third two rows 38, 39 of pipes. As illustrated in FIG. 8, the second row 39 of pipes of the third two rows are placed on the mats 56 in nesting relation to the first row 38. Four spaced lashings 64 and nine spaced spacer bars 45 are placed on top of the third two rows 38, 39 of pipes. The first end lashing 42 is wrapped around the end portions 28 and 40 of the first and third two rows of pipes and secured by a buckle 44 sufficiently tight to apply a pinching pressure to the intermediate second two rows 32, 33 of pipes to resist shifting thereof, but with the pressure being insufficient to cause deformation or bending of the first and third two rows 26, 27, 38, 39 of pipes. The previously laid interior lashings 58 and 60 are secured across the top of the third two rows 38, 39 of pipes.

As illustrated in FIG. 9, the first row 46 of the fourth two rows 46, 47 of pipes is laid on top of the spacer bars 45 on top of the third two rows 38, 39 of pipes with end portions 46 abutting the other end F of the car G. Four longitudinally spaced slip-resisting mats 56 are placed on the first row 46 of the fourth two rows 46, 47 of pipes. As illustrated in FIG. 10, the second row 47 of pipes of the fourth two rows 46, 47 are placed on the mats 56 in nesting relation to the first row 46. Three spaced lashings 66 and nine spaced spacer bars 45 are placed on top of the fourth two rows 46, 47 of pipes. The second end lashing 50 is wrapped around the end portions 34, 48 of the second and third two rows 46, 47 of pipes and secured by a buckle 44 sufficiently tight to apply a pinching pressure to the intermediate third two rows 38, 39 of pipes to resist shifting thereof, but with the pressure being insufficient to cause deformation or bending of the second and fourth rows 32, 33, 46, 47 of pipes.

A first row 53 of a first pair 53, 55 of nesting top rows is laid on top of the top row 47 of the fourth pair of pipes and is centrally disposed between the ends E and F of the car G. Four spaced mats 56 are placed on the first row 53 (FIG. 11). The second row 55 of the first pair of top rows 53, 55 is then placed in nesting relation on the first row 53 with the mats 56 therebetween (FIG. 12). The previously laid unsecured lashings 62 and 66 are wrapped over the first pair of top rows and secured by buckles 44. Cross-retaining lashings 74 are wrapped around each pair of vertical posts P and secured by buckles 44.

A first row 57 of a second pair of top rows 57, 59 is placed on the spacer bars 54 in alignment with the first pair 53, 55 of the top rows and four spaced mats 56 are placed on this first row (FIG. 13).

The second row 59 of the second pair 57, 59 of top rows is placed on the mats 56 in nesting relation to the first row of the second pair and the previously laid unsecured lashings 63, 64, 68 are wrapped over the second pair of top rows and secured by buckles 44. Nine spaced spacer bars 53 and three spaced lashings 70 are laid on top of the second pair of the top rows, and cross-retaining lashings 74 are wrapped around each pair of vertical posts P and secured by buckles 44 (FIG. 14).

A first row 59 of a top pair 59, 61 of top rows is placed on the spacer bars 54 aligned with the other rows of the top rows and four spaced mats 56 are placed on this first row of the top pair of top rows. Cross-retaining lashings 74 are wrapped around each pair of vertical posts P and are secured by buckles (FIG. 15).

The second row, or top row, 61 of the top pair of rows is placed on the mats 56 in nesting relation to the first row of the top pair of rows and the previously laid unsecured lashings 66, 68, 70 are wrapped over the top row and secured by buckles 44. Cross-retaining lashings 74 are wrapped around each pair of vertical posts P and are secured by buckles 44 (FIG. 16) to complete the loading of the stack 20.

The spacer bars provide spaces between the pipes that are above and below each spacer bar, for ease of access in unloading of the stack. However, spacer bars do not provide a significant advantage with respect to shifting of the pipes and their use is optional.

The above description recites particular numbers of spacer bars, 30, 36 and 54, and mats 56, which numbers are optional. Preferably, but not necessarily, there are at least four spacer bars per row, and at least two mats per row, and use of mats between rows of pipes below the height of the end wails of the gondola car is optional.

In view of the aforesaid written description of the present invention, it will be readily understood by those skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications, and equivalent 

What is claimed is:
 1. A stack of rows of substantially equal length elongate elements arranged for disposition in a container having an intermediate length greater than the length of the elongate elements, said stack of elongate elements comprising: a first horizontal row or rows of elongate elements including a lowermost row of elements; a second horizontal row or rows of elongate elements stacked on top of said first row or rows and having end portions at one and extending beyond one end of the elements of said first row or rows of elements therebelow, and said first row or rows of elements having end portions at the other end thereof extending beyond the other ends of said second row or rows of elements thereabove thereby forming a stack having an overall length approximating the intermediate length of the container; and means for restraining significant relative lengthwise movement of said rows of elements in said stack.
 2. The stack of elongate elements of claim 1 characterized further in that said restraining means retains said elements in a stacked configuration.
 3. The stack of rows of elongate elements of claim 1 characterized further by: a third horizontal row or rows of elongate elements stacked on top of said second horizontal row or rows of elongate elements and aligned lengthwise with said first horizontal row or rows of elements, the elements of said third horizontal row or rows of elements having end portions aligned with said end portions of the elements of said first horizontal row or rows of elements, a fourth horizontal row or rows of elongate elements stacked on top of said third horizontal row or rows of elongate elements and aligned lengthwise with said second horizontal row or rows of elements, the elements of said fourth horizontal row or rows of elements having end portions aligned with said end portions of the elements of said second horizontal row or rows of elongate elements; and said means for restraining comprises a first laterally extending end lashing secured around said end portions of said first and third horizontal row or rows of elements, and a second laterally extending end lashing secured around said end portions of said second and fourth horizontal row or rows of elements.
 4. The stack of rows of elongate elements of claim 1 characterized further by a plurality of laterally extending intermediate lashings, at least one of said intermediate lashings extending under the lowermost row of said elements and over at least two rows of elements thereabove, at least another of said intermediate lashings extending over the topmost row of elements and under at least two rows of elements therebelow, and other intermediate lashings each secured around a plurality of rows of elements that includes one row of elements that is also secured within at least one of the other intermediate lashings.
 5. The stack of rows of elongate elements of claim 1 characterized further by a top row or rows of horizontal elements stacked on top of the other rows of elements and generally longitudinally centered with respect to the combined length of the rows of elements therebelow.
 6. The stack of rows of elongate elements of claim 3 characterized further by a top row or rows of horizontal elements stacked on top of the other rows of elements and generally longitudinally centered with respect to the combined length of the rows of elements therebelow.
 7. The stack of rows of elongate elements of claim 1 characterized in that said elements are cylindrical and of substantially equal length and at least two rows of adjacent elements are arranged in a nesting pair, and at least one mat of slip resisting material is positioned between the rows of said nesting pair.
 8. The stack of rows of elongate elements of claim 1 characterized further by spacer bars disposed laterally between at least two adjacent rows of elements to provide spaces therebetween, and said restraining means comprises at least one lashing extending laterally through said space and secured around a plurality of rows of elements.
 9. The stack of rows of elongate elements of claim 4 characterized further by spacer bars disposed laterally between at least two adjacent rows of elements to provide spaces therebetween, and said other intermediate lashings extend through said spaces.
 10. The stack of rows of elongate elements of claim 8 characterized further by a plurality of spaced spacer bars disposed laterally under the lowermost row of elements.
 11. A method of loading a stack of horizontal rows of elongate elements of substantially equal length in a container having a bottom and upstanding end walls spaced apart a distance greater than the lengths of the elements, said method comprising: loading a first horizontal row or rows of elements into said container with one end portion at one end thereof adjacent one end wall of the container and the other end spaced from the opposite end wall of the container; loading a second horizontal row or rows of elements into said container on top of said first row or rows of elements with an end portion at one end adjacent said opposite end wall of said container and the other end spaced from said one end wall of the container; and applying means for restraining significant relative lengthwise movement of said rows of elements.
 12. A method of loading a stack of rows of elongate elements of substantially equal length in a container having a bottom and upstanding end walls spaced apart a distance greater than the length of said elements, comprising: placing a plurality of spaced laterally extending spacer bars on said container bottom; placing a plurality of bottom spaced laterally extending lashings on said container bottom for subsequent lashing together of rows of elements; loading a first row or rows of elements into said container on said bottom spacer bars with one end portion at one end thereof adjacent one end wall of the container and the other end spaced from the opposite end wall of the container; loading a second row or rows of elements into said container on top of said first row or rows of elements with end portions at one end adjacent said opposite end wall of said container and the other end spaced from said one end wall of the container; loading a third row or rows of elements into said container on top of said second row or rows of elements with an end portion at one end adjacent said one end wall of said container and above said end portion of said first row or rows of elements and the other end spaced from said opposite end wall above said other end of said first row or rows of elements; securing one of said lashings around the end portions of said first and third row or rows of elements; loading a fourth row or rows of elements into said container on top of said third row or rows of elements with an end portion at one end adjacent said opposite end wall of said container and above said end portion of said second row or rows of elements and the other end spaced from said one end wall above said other end of said second row or rows of elements; and securing another of said lashings around the end portions of said second and fourth row or rows of elements.
 13. The method of loading a stack of rows of elongate elements of claim 12 characterized further in that before loading said second row or rows of elements, placing a plurality of longitudinally spaced spacer bars laterally on said loaded first row or rows of elements and placing a plurality of lashings between said spaced spacer bars, during at least some subsequent loading of rows of elements spacer bars and lashings are placed on top of previously loaded rows of elements, and during said subsequent loading of rows of elements said previously laid lashings are secured around a plurality of rows of elements including rows above subsequently laid lashings.
 14. The method of loading a stack of rows of elongate elements of claim 13 characterized further in that said subsequent loading of rows of elements includes loading a plurality of upper rows of elements generally centrally disposed between the container end walls.
 15. The method of loading a stack of rows of elongate elements according to claim 14 wherein the elements are cylindrical, said method further comprising laying a plurality of said elements in nested pairs while placing mats of slip resisting material between the rows in said nested pairs. 